Light-based networks could replace wires for hospital patients

Visible light, using LEDs, could make patient monitoring via wires redundant.


Interference has been a major issue when hospitals have tried to replace the cluttered, bulky wiring used to monitor patients’ conditions—those are the wires protruding from a body, along with the associated beeps, as seen in the hospital TV drama procedurals we know and love.

Hard-wiring, though, has never been an ideal solution for biomedical signals—it prevents patients from moving around, for one thing. That ties up expensive hospital beds.


RF interference can not only interfere with other signals, but it can apparently damage hospital equipment, say some researchers in South Korea.

Those researchers, from Pukyong National University in Busan, reckon that they have a better solution. They want to use light instead.

Visible light

Li-Fi, or visible-light communications (VLC), could be a better solution if it can be made to work accurately. The researchers say they’ve gotten it to transmit signals from an electroencephalograph (EEG) over 50 centimeters. Their findings were published in IEEE Sensors Journal.

An EEG measures brain activity along the scalp. Voltage fluctuations are monitored from the neurons of the brain.


The team used LEDs' line of sight to communicate the EEG signals.

The transmitter consisted of RGB LEDs, and the receiver used three photodiodes with red, green, and blue filters.

Photodiodes are semiconductors that convert light into current—photons are absorbed by the diodes.

“It’s a very much friendlier means of transmitting biomedical signals in a hospital,” Yeon Ho Chung, an engineer at the university, said in an IEEE Spectrum report.

Weak signals

The EEG signals were relatively weak, Chung said in the IEEE article. Power ranged from one half to 100 millivolts, and frequencies between one half and 45 hertz. So the signals had to be amplified.

Distortion was also an issue, according to the article. That’s where the filters came in. The group used them to match each of the three LED colors, thus eliminating bit errors.

“You have to be very accurate. You can’t make any mistakes in transmitting,” Chung said, according to the report.

Other hospital monitoring

Brain monitoring with EEGs isn’t the only successful demonstration of Li-Fi in a hospital environment, the publication says. Electrocardiogram (EKG) readings have also been obtained with light by fellow scientists of the EEG team.

EKGs measure electrical activity in the heart and are used for finding health problems. The instrument displays results as spikes and dips in line tracings.

Communications for paralyzed patients

Electrooculography (EOG), a measurement of differences between the back and front of the eye, could also potentially use the same visible light communication technique.

It’s used for eye diagnosis, but can also be used for detecting eye movement. Thus, it could conceivably be used by paralyzed individuals for communication—without hindering wires, IEEE Spectrum says.

What happens to our TV shows?

But the big question, obviously, and without wanting to sound too facetious about this important and potentially life-changing invention for some, is what’s going to happen to the TV procedural’s dramatic effect, when there aren’t any wires sticking out of the patients and they’re nonchalantly walking around the ward?

There’s the drip still. And, hopefully, we’ll still have the dramatic beeps.

Copyright © 2015 IDG Communications, Inc.

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